|Reference: "Models of Vocal Fold Oscillation" NCVS Website (http://www.ncvs.org/ncvs/tutorials/voiceprod/tutorial/model.html)|
I hope you are all well and enjoying the start of the summer season. As I last indicated to you in a previous post, I am now living in Salt Lake City until August. Currently, I am learning about the principles of voice production from the father of Vocology in the states, Dr. Ingo Titze. The last two weeks have been an absolute blur of physics equations, understanding formant frequencies of non-uniform tubes and how to maximize resonance, semi-occluded vocal tract exercises (humming, straw exercises, anything where your mouth is almost closed) and the use of back pressure in these exercises to decrease the force of vocal fold adduction (coming together) during warm-ups.
What I find most interesting is how there is physical rationale for why we do some of the abstract things we do when we sing. There is also some debunking of myths in lecture. Each day I feel like I'm given a new lens in which to perceive some of these acoustic phenomena, but often, I just end up with more questions, which is what I find most satisfying because I am an academic at heart. This class really is like utopia for a speechie-chorister.
The next paragraph is a complete physics geek-out section. Feel free to skip if Physics is not your thing. You have been warned.
For example, I came to realize that I didn't even understand the basics of vocal fold vibration properly. I've been taught Bernoulli's Principle as the model for vocal fold vibration, but I learned that that is not the case. The Bernoulli's Principle does not explain the self-sustained oscillation of vocal fold vibration. All Bernoulli states is that when there is high velocity, there is low pressure and vice versa. However, if this was the only force in the vocal folds, these two forces would cancel out. It does not explain how there is continuous vibration of the vocal folds from an input air source. Instead we need to think of the vocal folds like a mass-spring system so when there is a build-up of subglottal pressure from our lungs in our glottis (space between the vocal folds), it creates a positive pressure in our vocal folds. This positive pressure is what pushes our vocal folds apart. What we also need to know is that even before we start phonating there is air already in our air tract above the vocal folds that is equal to atmospheric pressure (because from our lungs to the atmosphere we are essentially an open tube to the world). Thus, when air from our lungs meets this existing air that's already in the air tract (above the vocal folds), the air doesn't accelerate right away. The air in our air tract has it's own mass and inertia which is also why there is a positive build-up of pressure in our vocal folds that pushes the vocal folds apart. The vocal folds act like a recoil spring (due to be ratio of elastin, collagen, and muscle fibers in the different layers of our vocal folds) after the positive pressure in the lungs pushes them apart and they recoil back to their initial position. Then since there is continuous phonation pressure from our lungs, it starts this oscillation cycle once again. I applaud you if you were able to follow me through my verbose rationale. If you're intrigued by this model of vocal fold oscillation check out this tutorial link to learn more.
So you my be thinking, who cares how vocal folds vibrate? All I need to know is that they do and it doesn't make my performance any different. True, that may be the case. However, I feel like to use any system effectively, learning the mechanics can help with efficiency. For example, in terms of vocal fold vibration, there are certain threshold pressures from our lungs that need to be present in order to begin vibration. Singers that have a "pressed" voice quality are pushing so much air from their lungs and adducting their vocal folds together too strongly; thus, beginning a very damaging and high-impact vocal fold vibration. The vocal folds have a layered structure and when there is stress and tension on the epithelium (the top/cover layer of the vocal fold muscle) this can cause edema. For example, when there is any shouting, yelling or overall vocal abuse. When there is a build-up of fluid, just like those with arthritis can have a build-up of fluid in their joints, the extra fluid in the vocal fold tissues affect the efficiency of vocal fold vibration and this will be perceptible to a listener as a rough voice. I'm sure many of you already know that singing with a pressed voice means that you are working too hard, but I find it satisfying to know why in terms of a vibration model. I like to know why we do the things we do. Thus, doing voice exercises with easy and soft onsets is a way to reduce the overadduction (squeezing together) of our vocal folds.
I feel like with each of my lectures I could compose numerous posts. While I do intend to share more of what I learn with my readers, I think it is good to self-evaluate why we do the things we do. Conductors and teachers are aware (I hope...) of their rationale for choosing specific warm-up exercises. But as a singer/chorister, it is so easy to become complacent and just follow along without really understanding why we are doing particular exercises. Just like with any rehab treatment you want a therapist to use methods with evidence supporting its use. I feel that singing should be the same way. Of course, there are not the same amount of studies done on which exercises are effective or not, but we need to critical consumers of what we are doing in practice and learning more about an area is a way to do that. As informed singers, I feel like we should understand our instruments. When a violin player breaks a string, they know how to re-string and re-tune. I feel like a singer should be able to do the same. Or at least identify what it is in their regime that caused the difficulty to begin in the first place. The first step is knowledge. That is what I intend to continue pursuing while I am here.
Until next time readers, take care!